Vitamin B12 (Cobalamin) is named the "red vitamin," as it is a red crystalline compound. B12 is unique in that it is the only vitamin that contains an essential mineral--namely, cobalt. Cobalt is thereby needed to make B12 and so is essential for health. B12 is unique also in that it is required in much tinier amounts than the other B vitamins. Only 3-4 mcg(micrograms, or thousandths of a milligram) are needed at minimum; however, higher levels, up to 1 mg, are often used therapeutically.

Vitamin B12 is a very complex molecule. Besides cobalt, it also contains carbon, oxygen, phosphorus, and nitrogen. Cobalamin is stable to heat, though sensitive in heated acid or alkali solution, slightly sensitive to light, and destroyed by oxidizing and reducing agents and by some heavy metals.

Vitamin B12, a member of the B-complex vitamins, is a water-soluble vitamin that is stable to heat. It slowly loses its activity when exposed to light, oxygen, and acid or alkali environments. Loss of activity from cooking is approximately 70%. The main cobalamins in humans and animals are hydroxocobalamins, adenosylcobalamin, and methylcobalamin, the last two being the active coenzyme forms. Cyanocobalamin is widely used clinically, because of its availability and stability, and is transformed into the active factors in the body. Vitamin B12 is produced commercially from bacterial fermentation.

Vitamin B12 is necessary for the formation of blood corpuscles, nerve sheaths, and is involved in protein, fat, and carbohydrate metabolism. Adenosylcobalamin is the coenzyme for the isomerization of 1-methylmalonyl coenzyme A to succinyl Co A (an important reaction in lipid and carbohydrate metabolism) and in ribonucleotide reduction (which provides building blocks for DNA synthesis). Reactions involving methylcobalamin include biosynthesis of methionine, methane, and acetate. Vitamin B12 is required for the synthesis of folate polyglutamates (active coenzymes required in the formation of nerve tissue) and in the regeneration of folic acid during red blood cell formation. Vitamin B12 is better absorbed when combined with calcium, taken with several meals during the day, and during pregnancy. Absorption decreases with age and with deficiencies of vitamin B6, calcium, and iron. After absorption, vitamin B12 is bound to serum proteins (globulins) and is transported in the bloodstream to tissues.

cobalamin is needed in the manufacture of red blood cells and the maintenance of red blood cells and it stimulates appetite, promotes growth and releases energy. It is often used with older people to give an energy boost, assist in preventing mental deterioration and helps with speeding up thought processes. Some people are also of the opinion that it helps with clearing up infections and provide protection against allergies and cancer. This vitamin is also used in the metabolism of fats, proteins and carbohydrates.

Some symptoms of a deficiency will include a sore tongue, weakness, fatigue, and weight loss, back pain and apathy. It might further result in loss of balance, decreased reflexes, tingling of the fingers, ringing in the ears etc. A deficiency may also result in the raising of the level of homocysteine in the blood. Homocysteine in high doses can be toxic to the brain, which may be involved in Alzheimer's disease. Severe deficiency may result in pernicious anemia also called Addisonian pernicious anemia. Another problem that appears in deficiency is the eroding of the myelin sheath - the fatty sheath of tissue, which insulates the nerve fibers in your body.

People on strict vegan and macrobiotic diets are often deficient on Vitamin B12. Some people suffer from a potentially serious problem, causing the vitamin not to be absorbed in the intestinal tract, which can lead to pernicious (destructive) anemia. Anybody consuming alcohol should look at their B12 levels or if you take laxatives or antacids regularly. Older people could also benefit from this vitamin as the intestinal situation changes as you age, and many people older than sixty have difficulty extracting the vitamin from ingested food since the correct stomach acids are not present.

Vitamin B12 is present in liver, organ meat, muscle meat, shellfish, eggs, cheese, fish, and can be manufactured in the body. Although milk contains B12, processing of milk may lead to destruction of the vitamin.

Vitamin B12 can not be manufactured by any plants. It is only found in animal products; therefore a deficiency may happen to people on a strict vegan diet. Unlike other water-soluble vitamins, B12 needs some 3 hours to be absorbed where other B vitamins are absorbed almost immediately.